There have been known gravity compensation elevators using gas pressures, which are adapted to generate a vertical force balanced with the gravity acting on a load object, using a gas cylinder, for enabling ascending and descending the object with a weight, with the same feeling as that in a non-gravity environment in order to facilitate loading operations of the object with the weight. As such gravity compensation elevators, there have been known arm-type elevators, hoist-type elevators, and the like. Such arm-type elevators are adapted to vertically support an arm movable in a horizontal direction with a gas cylinder and, further, are adapted to balance the weight of a load object being grasped by the tip end of the arm, with the force generated from the gas cylinder. Such hoist-type elevators are adapted to convert the force generated from a gas cylinder held movably in a horizontal direction, into a rotational torque, using ball screws and the like, and, further, are adapted to utilize it as a force for winding up a wire for balancing the weight of a load object therewith (refer to Patent Literature 1 and Patent Literature 2, for example).